Differential roles of gestures on spatial language in neurotypical elderly adults and individuals with focal brain injury.

Gestures might serve communicative functions by supplementing spoken expressions or restorative functions by facilitating speech production. Also, speakers with speech deficits use gestures to compensate for their speech impairments. In this study, we examined gesture use in speakers with and without speech impairments and how spoken spatial expressions changed when gestures were restrained. Six patients with speech problems and with left frontal and/or temporal lesions and 20 neurotypical controls described motion events in 3 different conditions (spontaneous gesture, only speech, and only gesture). In addition to the group analyses, we ran case analyses. Results showed that patients used more gestures compared to controls. Gestures served both communicative and restorative functions for patients whereas controls only used gestures for communicative purposes. Case analyses revealed that there were differential patterns among patients. Overall, gesture production is multifunctional and gestures serve different functions for different populations as well as within a population.